Poet not good while playing (6)
I believe the answer is:
larkin
'poet' is the definition.
(Philip Larkin)
'not good while playing' is the wordplay.
'not good while' becomes 'lark' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'playing' becomes 'in'.
'lark'+'in'='LARKIN'
Can you help me to learn more?
(Other definitions for larkin that I've seen before include "English poet, 1922-85" , "Philip ---, C twenty English poet" , "Coventry-born poet associated with Hull" , "Cab" , "See 15" .)